Abstract: The estimation error of the time difference of the frequency hopping signal in the spread spectrum communication network is too high, leading to a decrease in signal positioning and tracking ability, and signal propagation stagnation in multiple fields. In order to enhance the propagation efficiency of the frequency hopping signal in the spread spectrum communication network and improve the signal detection ability of the radiation source tracking and positioning system. A method for estimating the time difference of hopping signals in spread spectrum communication networks is proposed based on FRFT ( Fractional Fourier Transform ) and blind separation. The blind separation method is used to obtain two channels that meet the time difference estimation conditions of frequency hopping signals, namely flat fading channel and frequency selective fading channel. The two channel characteristics are estimated by FRFT. The time difference estimation of frequency hopping signals in spread spectrum communication networks is realized by combining the characteristics of flat fading channel and frequency selective fading channel with the maximum likelihood block detection algorithm. The experimental results show that the root mean square error of the proposed method is at a low level and the estimation success rate is at a high level whether in normal environment or noise interference environment.

Key words: blind separation; , flat fading channel; , frequency selective fading channel; , fractional fourier transform(FRFT); , time difference estimation